Stereoscopic telemeter.



y C. VON HOPE. STEREOSGOPIG TELEMETER.

APPLICATION FILEB JUNE 18, 1907. RENEWED DBO. 8,1908.

Patented Mar. 9, 1909.

.l Il IVI/Iliff UNITED STATES PATENT oEEIoE.

CHRISTIAN .VON HOFE, OF JENA, GERMANY, ASSIGNOR TO THE FIRM OF CARL ZEISS, OF

JENA, GERMANY.

STEREOSCOPIC TELEMETER.

Specification of Letters Patent.

Patented March 9, 1909.

Application filed June 18, 1907, Serial No. 379,564. Renewed December 8, 1908. Serial No. 466,507.

'Ihe invention relates to both kinds ofstereoscopic telemeters described in the Patent 583,703, the one known as the fixed scale type. and the other as the traveling mark type. But of these instruments only those are improved by the invention the base line of which is a multiple of the distance between the .oculai-S, so that their casing consists chiefly of a tube transverse to the line of sight, and in which the adaptation ofthe distance between the oculars to the interpupillary distance in connection with the maintenance or restoration of the sharp focus ofthe oculars is eected by vmeans of appliances for altering the position'of hinder parts of the telescope in the sighting plane. 'lelemetersof this species have hitherto been constructed so that the two image fields containing the physical components of the stereoscopic scale or mark follow the ocular prisms and recede the Ramsden oculars which lie in t e direction of sight, and further so that the oculars, ocular prisms and measuring marks can be moved in contrary directions along the transverse tube, the

oculars alone, however, being movable in the,

direction of their axes.

The resent llnprovement has arlsen fromthe fo owmg knowledge. From the fact Vthat thesaid component marks are movable parts of the telescope or are placed behind such a movable part the danger is to be apprehended, that a relative displacement of the component marks and of the image field containing them, that is to say deran ement of the instrument, is liable to happen t rough accidental alteration of position of one movable part of the telescope. According to the present invention this drawback is removed y transferring the component marks into the transverse tube, that is to sa into image fields, the axes of which have tlie direction of the transverse tube, securing them there and at the same time` making onl parts lying behind them mvable. If t is improved arrangement fory ada ting the distance between the oculars to t e inter-pupil- -lary distance be adopted in an instrument With terrestrial ocular-s, of the two image fields of each of which at least the front one lies in the transverse tube, it is possible to maintain the sharp focus without special shifting of telescope parts. For this urpose the said front image fields are provided with the component marks, the reversin y system of the terrestrial ocular is divided intoV two separate component systems in cils are formed by parallel rays, at least the front component system is arranged in the transverse tube, and the hinder component system with-telescope parts following it is 1made s'hiftable in the direction of the base In the accompanying drawing: Figure 1 is a horizontal section alon the sighting plane through a stereoscopic te emeter of the fixed scale type constructed according to the invention, some optical parts being shown in lan view 'for the sake of clearness. Fig. 2 is a iorizontal section through a modified telemeter. Fig. 3 is a horizontal section through another modified telemeter. Fig. 4 is a face view of the left one of the two transparent lates carrying the component mark systems rom which in each of the three telemeters the stereoscopic scale originates.

the instrument is quite symmetrical, also in the sense, that in ada tation to the interpupillary distance bot telescopes undergo equal alterations.

The stereoscopic telemeter accordingI to Fig. l shows the transparent carriers a a of the component marks, secured in the transverse tube b, so that the component marks, which may be arranged in several rows as shown in Fig. 4 lie in the image fields of the objectives -c c. Between each carrier aI and the ocular d appertaining to it a simple reflecting prism e is arranged. The objective prism f placed before each objective c resents to the entering rays first a simp e refiecting surface, whose eHect on the image is afterward annulled by the ocular prism e, after that, however, a ridge surface f", the image-inverting effect of which cancels that of the objective c. To adapt the distance between the oculars to the inter-pupillary distance, the ocular prisms e e are secured upon slides g g, which can be moved in opposite directions by means of a pinion h operated from below such a manner, that between them the pen- In all three 'examples the arrangement of the tube t. Upon each slide, van ocular tube do is guided in the direction of its Vaxis and and therefore the sharp focus of the ocu ars.

' is likewise maintained.

In the telemeter according to Fig. 2, in order to erect the inverted image, which is projected by the objective c upon the place of the carrier a of vthe component marks, a terrestrial ocular is provided, consisting of the collective lens i, an inverting system the components of which are k and l, and the ocular d proper, which is arranged behind the erect second image indicated by m. The lenses i and 7c are chosen, so that the encils leave 7c in parallel rays. The lens from which these pencils are received, is in the present example arranged only behind the' ocular prism e. It suffices in this case (and also if the lens Zwere placed before the ocular prism e) to x l and e together with the ocular tube do upon the slide g, since the ocular prism e does not alter the cylindrical form of the encils, and the image, on which the ocular d is focused, in consequence maintains its position at m during the shifting of the slide g. Simple reflecting prisms n can be' arranged as objective prisms. j

The arrangement of the instrument according-to Fig. 3 has this advantage above the one according to Fig. 2, that the oculars do not roject so far beyond the transverse tube. his arrangement can be considered as having taken its origin from Fi 2 as follows; Instead of a real image eing observed through the ocular d, a negative lens o as in the Galilean telescope is made use of as ocular, but which entails a further inversion of the image. In order to resent to the observer an erect image notwit standing, the two defiecting piisms of each telescope considered as a whole are here as in Fig. 1 fitted with one inverting ridge and two simple reflecting surfaces, only-that this time the ridge is given tothe ocular rism and the objective prism g' is shaped l1 e a Prandtl prism. The situatlon of the lens Z behind the ocular prism, as in Figs. 2 and 3, also allows of fixing this prism in the transverse lensl is then, however, necessary, so as to enable this lens, with lany adjustment of the telemeter to the inter-pupillary distance, to transmit all rays leaving the prism e to the ocular.

I claim:

1. A stereoscopic telemeter consisting of two telescopeseach comprising an objective prism system and an ocular prism system, which four rism systems are fitted in a transverse tu e forming the main casing, an objective, an ocular and a component mark system which is fixed in thetransverse tube, such of the said optical parts, which lie behind the component markl system and form the hindmost portion, being movable for the purpose of adapting the distance between the oculars to the inter-pupillary distance and maintaining or restoring the focus of the oculars.

2. A stereoscopic telemeter consisting of two telescopes each comprising an objective prism system and an ocular -prism s stem, which four rism systems are fitte in a transverse tu e formin the main casing, an objective, a terrestria ocular, the imageerecting system of which consists of two separated components, between which the encils are formed of parallel rays and ofw ichl the front component is fixed in the transverse tube and the back com onent together with the following parts o the terrestrial ocular and with the ocular 'rism system is movable for adapting the dlstance between the terrestrial oculars to the inte'r-pupillaryv distance, and a component mark system fixed in the transverse tube inthe front image field of the terrestrial ocular.

CHRISTIAN VON HOFE.

Witnesses:

PAUL KRUGER, FRrrz SANDER.

tube and only leaving the lens l and the ocular u on the slide g. A somewhat larger. 

